Case Presentation: A 67 year old man with a history of well-controlled HIV (undetectable viral load, CD4 509 cells/µL) presented with two days of progressive weakness and malaise. He was walking his dog when the weakness worsened, leading to a fall. On arrival to the emergency department, his vital signs were notable for SpO₂ 89%, heart rate 133/min, temperature 101.9°F, respiratory rate 35/min, and blood pressure 89/53 mm Hg. He was ill-appearing and diaphoretic. Labs showed WBC 14.8 × 10⁹/L, creatinine 1.97 mg/dL, lactate 6.7 mmol/L, CPK 8,651 U/L, and urinalysis noted pyuria and hematuria. CT abdomen/pelvis showed a fluid-filled bladder and mild bilateral hydronephrosis. He received IV fluids, cefepime and vancomycin with improvement in hemodynamics and was admitted with severe sepsis, suspected to be of urinary source and was started on ceftriaxone. By day 3 of hospitalization, urine culture was negative and blood cultures grew gram-negative rods in two anaerobic bottles at 61 hours of incubation. Fevers continued, but the patient remained otherwise clinically stable. On day 7, Capnocytophagia canimorsus was identified on blood cultures and antibiotics were adjusted to Ampicillin/Sulbactam. Transthoracic echocardiography showed no valvular abnormalities and repeat blood cultures were negative. The patient was slow to improve but ultimately defervesced and was discharged home on Amoxicillin/clavulanate to complete a 14-day course.
Discussion: C. canimorsus is a gram-negative rod found in dog and cat oral flora. Though human infection is rare, with an incidence of 0.67 cases per million population, it has a mortality rate of 10-30% following animal bites or scratches (4,6). Infections can present with severe sepsis, coagulopathies, multi-organ failure, meningitis, or cellulitis (1,3,6). Risk factors include asplenia, alcoholism, immunosuppression, male sex, and age >50 (1,2). This patient with well-controlled HIV presented with severe sepsis from C. canimorsus complicated by rhabdomyolysis and acute kidney injury (AKI). This case shows that C. canimorsus infection can occur despite limited risk factors. The patient denied dog bites or scratches, indicating that routine or close contact with a dog may be enough for transmission. AKI is common in reported cases; however, rhabdomyolysis has not been described. Only one prior case in a HIV patient has been reported (with aortitis) (5), making the degree of vulnerability in this population unclear. The patient’s clinical course illustrates the importance in maintaining a broad differential. Imaging and urinalysis indicated a urinary source, but the negative urine culture and persistent fevers suggested an alternative diagnosis. Frequent reassessment, early broad-spectrum antibiotics, and prompt adjustment to treatment were key. These steps may have prevented further deterioration and avoided an ICU course. Given the slow growth and high mortality associated with C. canimorsus bacteremia, clinicians should maintain suspicion with any dog exposure.
Conclusions: C. canimorsus infection should be considered in those with close contact with dogs, even without other significant risk factors. This case demonstrates the wide spectrum of clinical manifestations, with rhabdomyolysis not previously recognized. Early broad-spectrum antibiotics are critical given the bacteria’s slow growth and high mortality rate. Careful avoidance of diagnostic anchoring and routine reassessment were key in preventing clinical deterioration in this patient.